FMEA严重度、频度、探测度系数选择DFMEA：
推荐的ＤＦＭＥＡ严重评价准则
风险顺序数（RPN）风险顺序数是严重度（S）、频度（O）和探测度（D）的乘积。
RPN=（S）X （O）X （D）
在单一FMEA范围内，此值（1-1000）可用于设计中所担心的
事项的排序。
PFMEA
推荐的PFMEA探测度评价准则
风险顺序数风险顺序数（RPN）是严重度（S），频度（O）和探测度（D）的乘积。（RPN）（S）X（O）X（D）=RPN
探测性评价准则：由设计控制可探测的可能性探测度探测可能性没有探测没有现行探测，无法探测或未分析10 几乎不可能在任何阶段都不易探测设计分析/探测控制的探测能力很弱；虚拟分析与预期的实际操作条件 没有关联 9 很微小 在设计定稿后，设计发布之前使用通过/不通过试验(用接受标准测试如: 乘坐与操纵) 8 微小使用试验到失效进行产品确认(直到发生故障) 7 很低使用老化试验进行产品确认(耐久性试验后的功能试验) 6 低 在设计定稿前使用通过/不通过试验(性能接受标准,功能检查) 5 中等 使用试验到失效进行产品确认(直到发生泄露、破裂等) 4 中等偏高 使用老化试验进行产品确认 3 高 虚拟分析相关设计分析/探测控制的探测能力很强；虚拟分析与预期的实际操作条件 关联性很高 2 很高 失效预防有设计方案（已证实的设计标准）的充分预防，失效原因或模式无法发 生
发生可能性频度数原因的发生频度-DFMEA（在项目或汽车的可靠性/设计寿命内）可能失效率 很高10 没有前期历史的新技术/新设计＞=100/千辆/项高9 在工作循环/操作条件内，对于新设计，新应用或变更，失效不可避免50/千辆/项 8 在工作循环/操作条件内，对于新设计，新应用活变更，失效是可能的20/千辆/项 7 在工作循环/操作条件内，对于新设计，新应用活变更，失效是不确定的10/千辆/项 中等 6 相似设计，或者在设计模拟/测试时的频繁失效2/千辆/项 5 相似设计，或者在设计模拟/测试时的偶尔失效0.5/千辆/项 4 相似设计，或者在设计模拟/测试时的个别失效0.1/千辆/项低 3 几乎相同设计，或在设计模式/测试时仅有个别失效0.01/千辆/项 2 几乎相同设计，或在设计模式/测试时没有观测到失效0.001/千辆/项 很低 1 通过预防控制消除失效通过预防控制消除失 效
过程失效模式分析 P F M E A PFMEA P F M E A : / : // / .A B C .. .,, .(. )(/) ( ( ) ) 10 9 8 7 6 5 4 3 2 1 10 9 8 7 6 5 4 3 2 1 10 9 8 7 6 5 4 3 2 1 /100 ,1000 X , , : /50 , , , 1000 1000 1000 1000 1000 1000 1000 1000 X X X X 100% 1 , / / / ()20 10 5 : .,(100%) , 0.5-1 , , / / (100%) ,,S P C( ) ., , , X X X X X 0.5 /100%,, : 2 X X X X X 100%/ / / / .,,(, 1 (75%)100%) () , : . . (100%) , 0.5 0.1 , , 50%, : (100%) ,, (25%) :/ 0.01 ,1000 : A = ·B =·C =
P R O C E S S F M E A Suggested PF M E A Severi ty Evaluat ion Cr i te r ia Sugges ted PFMEAOccur rence Eva l ua t i on C r i t e r i a Suggested PF M E A Detect ion Evaluat ion Cr i ter ia Cri ter ia : Sever i ty o f Ef fec t : Th is rank ing r esul ts when a potent ia l fa i lu re mode resu l ts in a f ina l custo mer and/or manufactur ing/asse mbly p lant defect . The f ina l custo mer should a lways be cons idered f i rs t . I f both occur , use the h igher o f the two sever i t ies . Probabi l i ty Ef fect R anking Like ly Fa i lure Rates R anking D etect ion Cri ter ia A B C Suggested Range o f Detect ion Methods R anking of Fa i lure (Custo mer Ef fec t ) (Manufactur ing/Asse mbly Ef fec t ) Very h igh sever i ty rank ing when a potent ia l fa i lu re mode af fec ts safe vehic le operat ion and/or invo lves nonco m pl iance wi th govern ment regula t ion wi thout warn ing. Absolute H azardous wi thout Or may endanger operator (machine or asse m bly) wi thout warn ing. 100 per thousand Al most Imposs ib le cer ta in tynon- of detect ion. 10 9 10 9 10 9 X C annot detect or is not checked. pieces W arning Very High: Pers is tent fa i lu res Very h igh sever i ty rank ing when a potent ia l fa i lu re mode af fec ts safe vehic le operat ion and/or invo lves nonco m pl iance wi th govern ment regula t ion wi th warn ing. H azardous wi th C ontro ls wi l l Or may endanger operator (machine or asse m bly) wi th warn ing. C ontro l is ach ieved wi th ind i rec t orrando m checks on ly . 50 per thousand p ieces Very Re m ote probably not detect . X W arning Or 100% o f product may have to be scrapped, or veh ic le /i tem repai red in repai r depar tment C ontro ls Vehic le /i tem inoperable (loss o f pr imary funct ion). C ontro l is ach ieved wi th v isual inspect ion only . 8 7 8 7 8 7 Very High High 20 per thousand p ieces 10 per thousand p ieces R e m ote have poor chance of C ontro ls X X High: Or product may have to be sor ted and a por t ion (less than 100%) scrapped, or vehic le /i tem repai red in repai r depar tment wi th a repai r t ime between hal f an hour and Frequent fa i lu res Vehic le /i tem operable but a t a reduced leve l o f per formance. C usto mer very d issat is f ied. have poor chance of detect ion. C ontro l is ach ieved wi th double v isua l inspect ion on ly . Very Low Or a por t ion (less than 100%) o f the Vehic le /i tem operable but co mfor t / p roduct may have to be scrapped wi th no C ontro l is ach ieved wi th char t ing m ethods, such as SP C (Stat is t ica l Process Cont ro l ). C ontro ls may detect . 6 6 6 M o derate convenience i te m(s) inoperable . C usto mer d issat is f ied. sor t ing, or veh ic le /i tem repai red in repai r depar tment w i th a repai r t ime less than hal f an hour . 5 per thousand p ieces Lo w X X Vehic le /i tem operable but co mfor t / Or 100% of product may have to be convenience i te m(s) operab le reworked, or veh ic le /i tem repai red o f f -l ine at a reduced leve l o f per formance. but does M o derate : O ccasional fa i lu res C ontro l is based on var iab le gauging af ter par ts have le f t the s ta t ion, O R G o/No Go gauging per formed on 100% of the par ts a f ter par ts have le f t the Error detect ion in subsequent C ontro ls may detect . 5 4 5 4 5 4 Lo w 2 per thousand p ieces 1 per thousand p ieces M o derate X X X X C usto mer so me what d issat is f ied. Fi t & f in ish/squeak & ra t t le i tem does not conform. Defect not iced by most custo mers (greater than 75%). not go to repai r depar tment . C ontro ls Or the product may have to be sor ted, wi th no scrap, and a por t ion (less than 100%) reworked. have a good chance to detect . operat ions,O R gauging per formed on setup and f i rs tp iece check (for setup causes on ly). Very Low M o derate ly High Error detect ion in-s ta t ion, O R error detect ion in subsequent operat ions by m ul t ip le layers o f acceptance: supply , select , ins ta l l ,ver i fy . Can not accept discrepant par t . C ontro ls Fi t & f in ish/squeak & ra t t le i tem does not conform. Defect not iced by 50% of custo mers. Or a por t ion (less than 100%) o f the product may have to be reworked, w i th no scrap,on-l ine but out -o f -s ta t ion. have a good chance to detect . 3 3 3 Minor 0.5 per thousand p ieces 0.1 per thousand p ieces High X X X Lo w: R elat ive ly few Fi t & f in ish/squeak & ra t t le i tem does not conform. Defect not iced by d iscr iminat ing custo mers (less than 25%). C ontro ls almost fa i lu res Or a por t ion (less than 100%) o f the product may have to be reworked, w i th no scrap, on l ine but in -s ta t ion. Error detect ion in-s ta t ion (auto mat ic gauging wi th auto mat ic s top 2 1 2 1 2 1 Very Minor N one Very High Very High X X cer ta in to detect . feature).Can not pass d iscrepant par t . R e m ote: Fai lure is unl ike ly C ontro ls cer ta in to detect . Discrepant par ts can not be made because i te m has been er ror proofed by process/ product des ign. Or s l ight inconvenience to operat ion or operator , or no e f fec t . 0.01 per thousand pieces N o d iscern ib le e f fec t . Inspect ion Types: A = Error Proofed · B = Gauging · C = Manual Inspect ion